Adolescence is crucial for optimizing future bone health because bone accumulates rapidly during these years and accounts for up to half of adult peak bone mass (PBM), which is a strong predictor of bone fragility later in life. Calcium intake during this period is critical for adequate bone mineralization; if low, it could lead to low bone mass and increased risk of fractures. Calcium is the nutrient most deficient in the diets of US adolescents, with only 30% meeting the recommendation. A strategy to maximize bone mineralization in adolescence is to increase calcium absorption, which could be achieved by supplementation with non-digestible carbohydrates, such as soluble corn fiber (SCF). SCF is fermented by gut bacteria producing short-chain fatty acids, which improves absorption of minerals and could decrease bone resorption. Studies in rats show that SCF is the fiber that results in the greatest bone mass and resistance to fractures compared to other fibers. The few studies in humans show that supplementing adolescents with SCF results in the greatest increase in calcium absorption but it is not known if this translates into an increase in bone mass, particularly during the period of adolescence growth spurt. Therefore, the primary aim of this proposal is to determine the effects of SCF supplementation for 1 year on bone metabolism in growing adolescents compared to placebo. For the proposed study, a randomized double-blinded placebo controlled clinical trial will be conducted in 236 healthy adolescents aged 11-14 years, equally randomly assigned to one of four intervention groups: SCF (12 g/d), SCF + calcium (12 g/d of SCF + 600 mg/d of elemental calcium), placebo (0 g/d of SCF or of calcium), and placebo + calcium (0 g/d of SCF + 600 mg/d of elemental calcium); all administered twice a day. Bone mass will be assessed at baseline at 6 months and at 12 months and bone related biomarkers and fecal microbiome will be assessed at baseline and at 12 months. Assessment visits will be conducted in the Clinical Research Center of the Stempel School of Public Health at Florida International University. We will also have short home visits at 3 and 9 months to collect unused supplements and provide more supplements. Compliance will be evaluated at all visits and also in real time using a study mobile app. If supplementing diets with SCF lead to significantly higher bone mass in adolescence, this could help to achieve the genetic potential for PBM and to start adult life with stronger bones. Fortifying different food matrices or supplements with SCF may be a cost-effective intervention at the population level for bone health than increasing dairy products consumption, particularly in adolescents. Given that the antecedents to osteoporosis risk factors begin in childhood/adolescence and track into adulthood, intervening at these stages has tremendous potential as means for preventing osteoporotic fractures later in life and minimizing its economic impact.